1. Field of the Invention
The present invention relates to a reversible thermal-recording composite capable of forming and erasing image, and a rewritable reversible thermal-recording sheet and a rewritable thermal-recording card using the same; more specifically, the present invention relates to a rewritable reversible thermal-recording composite, being capable of yielding a high printing concentration even in the case of low electric power load and having excellent durability for repeated printing and long-term stability of image, and a sheet and a card using the same.
2. Description of the Prior Art
Out of concern for increased garbage output in metropolitan areas and for protection of wood resources and the like, the reduction of paper consumption has become increasingly desirable in recent years. Following the rapid expansion of computer industries, the consumption of OA paper is on the rise with no possibility of reduction, so that finding an alternative to paper consumption is a very urgent issue.
In such circumstances, the research and development works of a reversible thermal-recording composite material capable of forming and erasing image in a repeated manner have been carried out actively. Up to now, inventive disclosures have been made in the following publications;
(1) Japanese Patent Laid-open No. Sho 63-39377; PA0 (2) Japanese Patent Laid-open No. Sho 63-41186; PA0 (3) Japanese Patent Laid-open No. Hei 2-566; PA0 (4) Japanese Patent Laid-open No. Hei 2-1363 PA0 (5) Japanese Patent Laid-open No. Hei 2-80289; PA0 (6) Japanese Patent Laid-open No. Hei 2-81672; PA0 (7) Japanese Patent Laid-open No. Hei 2-86491; PA0 (8) Japanese Patent Laid-open No. Sho 58-191190; PA0 (9) Japanese Patent Laid-open No. Sho 60-193691; PA0 (10) Japanese Patent Laid-open No. Sho 62-255482; PA0 (11) Japanese Patent Laid-open No. Hei 4-14482; PA0 (12) International Patent Publication W090/11898; PA0 (13) Japanese Patent Laid-open No. Hei 4-46986; PA0 (14) Japanese Patent Laid-open No. Hei 4-50289; PA0 (15) Japanese Patent Laid-open No. Hei 4-50290; PA0 (16) Japanese Patent Laid-open No. Hei 5-92661; and the like. PA0 2-(2-chloroanilino)-6-diethylaminofluorane; PA0 2-anilino-3-methyl-6-dibutylaminofluorane; PA0 2-(2-chloroanilino)-6-dibutylaminofluorane; PA0 1,3-dimethyl-6-diethylaminofluorane; PA0 2-N,N-dibenzylaminodiethylaminofluorane; PA0 3-indolino-3-(p-dimethylaminophenyl)-6-dimethylaminophthalide; PA0 3-diethylamino-7-chlorofluorane; PA0 2-(2-fluorophenylamino)-6-diethylaminofluorane; PA0 2-(2-fluorophenylamino)-6-di-n-butylaminofluorane; PA0 3-diethylamino-7-cylohexylaminofluorane; PA0 3-diethylamino-6-methyl-7-anilinofluorane; PA0 3-diethylamino-6-methyl-7-p-butylanilinofluorane; PA0 3-cycIohexylamino-6-chlorofluorane; PA0 2-anilino-3-methyl-6- N-ethyl-p-toluidino)-fluorane; PA0 3-pyrrolidino-6-methyl-7-anilinofluorane; PA0 3-pyrrolidino-7-cyclohexylaminofluorane; PA0 3-N-methylcyclohexylamino-6-methyl-7-anilinofluorane; PA0 3-N-ethylpentylamino-6-methyl-7-anilinofluorane; PA0 3-cyclohexylmethylamino-6-methyl-7-anilinofluorane; PA0 3-ethylisobutylamino-6-methyl-7-anilinofluorane; PA0 3-propylmethylamino-6-methyl-7-anilinofluorane; and the like.
The contents described in the items (1) to (7) are characterized in that an organic low molecular substance is dispersed in an organic polymeric binder and the crystallization and polycrystallization of the organic low molecular substance is then reversibly promoted in the binder by thermal energy. Generally, the method for forming an image by utilizing the opaque phenomenon through polycrystallization has drawbacks such as insufficient contrast, which cause difficulty in visual observation.
The inventions disclosed in (8) to (10) comprise a coloring agent, a developer, and an organic polymeric binder, wherein printing is done at a thermal process but the erasing of the resulting printing requires water or steam The contents described in (11) relate to spontaneous erasing of printed image, wherein the control of printing and erasing is difficult.
The contents described in (12) to (16) comprise a leuco dye, a coloring and fading agent reacting with the leuco dye for coloring and fading, and an organic polymeric binder. Generally, a higher contrast along with ready visual observation can be yielded with such thermal composite, but the printability and erasability thereof are reduced if printing and erasing are repeated with such composite. From the respect of industrial application, therefore, the improvement of the durability for repeated printing has been desired greatly. According to the method, additionally, complete switching between coloring reaction and fading reaction cannot be attained under simple control of thermal energy, and both the reactions occur simultaneously at a certain ratio. Thus, satisfactory coloring and sufficient fading cannot be attained concurrently. Because the fading action of a basic group acts on a colored part at room temperature, a phenomenon such that the printing concentration of the colored part is decreased over time is never avoidable.
Therefore, the development of a reversible thermal-recording material, which can produce printing at a high contrast by routine printing process wherein the resulting printed characters can be erased simply through heating and the like and which can retain stable images for a long term in daily atmosphere and that has excellent durability for repeated printing has been greatly desired.